Turbulence strip for heat exchanger tubes



y 1954 H, F. BRINEN ETAL TURBULENCE STRIP FOR HEAT EXCHANGER TUBES Filed Sept. 12, 1951 INVEN fffi TORS.

gg d 0 ATTORNEY Patented May 4, 1954 TURBULENGE STRIP FOR HEAT EXCHANGER TUBES Howard F. Brinen and Fred M. Young, Racine, Wis., assignors to Young Radiator Company, Racine, Wis., a corporation of Wisconsin Application September 12, 1951, Serial N 0. 246,313

7 Claims.

This invention relates to turbulence or agitator strips for the tubes of fluid heat exchangers, particularly those used for cooling the oil required in high-powered diesel engines.

It is well known that in tubular heat exchangers the tendency toward the equalization of temperature between the fluid flowing through the tubes and that enveloping the tube takes place through the tube wall. Where the fluid is howing through the tube under pressure it is also well known that the column of fluid in effect comprises a concentric series of films or laminae from the core to the circumference coincident with the inner face of the tube wall. Under pressure these concentric films or laminae tend to move successively slower from the core outwardly to the circumference where the film or lamina in frictional contact with the inner face of the tube wall moves the slowest, in fact, tends almost to immobility. Obviously, therefore, under such conditions the heat dissipation of the tubular column. of fluids is successively less from the circumference inwardly to the core where the heat dissipation is at a very minimum. To overcome this decreasing heat dissipation from the wall of the tube inwardly to the core of the fluid columnit has been a common practice to incorporate in the tube some kind of a fin, bafile, or turbulence strip designed to slice or break up and axially deflect these concentric fluid films or laminae so as to effect contact of all the fluid molecules with the heat-disspating tube wall. However such agitator devices may facilitate the temperature drop they introduce the problem of pressure drop-sometimes impractically exces sive. Hence, the construction of such devices have followed a myriad of patterns in an attempt to get a reasonably high temperature drop with a minimum pressure drop of the agitated fluid flow through the tube.

With the advent of the high heat-creating en gines, such as diesels, particularly as used for electric locomotives, a new problem has been confronted in the use of tubular heat exchange equipment with agitators-the problem of cleanability. It is the practice with this type of power unit to give it a complete overhaul periodically. The complete overhaul of the oil heat exchangers requires the removal of the agitators so that they, as well as the tubes, may be flushed of all sludge and sediment, and after which the agitators are replaced in the tubes.

The tubular heat exchangers for equipment of this kind are made up of small-diameter, thin metal tubes. Ccnventionally, these are of copper or brass of less than one-half inch outside diameter. Moreover, such heat exchangers for these high-powered diesel electric locomotives have to be comparatively large units comprising hundreds of these small tubes. Heretofore, the agitators have been intended to remain permanently in the tubes. Accordingly, they have been formed of thin metal so as to afiord the most effective agitation with the very minimum of the decrease of volume within the tube. When such agitators were not bonded to the tubes, and therefore could be removed, they have been too light and flimsy to make practical the handling of them for removal, flushing and/or replacing.

The main objects of this invention, therefore,

. are to provide an improved form of agitator for small-diameter tubes of heat exchangers of sufficient rigidity to make highly practical their removal, their handling outside the tubes for flushing, and their subsequent replacement within the tubes; to provide an improved form of agita tor of this kind capable of achieving a most practical high-temperature drop with a concurrent low-pressure drop; and to provide an improved agitator of this kind which is so simple to manufacture as to make its production extremely economical.

In the accompanying drawings:

Fig. 1 is a perspective view of a section of an improved agitator embodying this invention;

Fig. 2 is a side elevation of an end section of such an agitator, the full and dotted arrow-head lines respectively indicating two of the oilflow paths which are believed to occur with the use of such an agitator in a tube;

Fig. 3 is a fragmentary, longitudinal, sectional View of a tube showing an agitator in place, the dot and dash arrow-head lines indicating the baffled oil flow believed to be created by the oppositely-disposed angularly-arranged lobes;

Fig. 4 is a, transverse, sectional View of the same taken on the line l4 of Fig. 3; and

Fig. "5 is a fragmentary, sectional detail taken on the line 55 of Fig. 2.

The distinctive concept of this invention involves an agitator strip with a spine section so formed as to possess a high degree of self-rigidity and having arcuate-shaped apertured lobes alternately struck out from opposite sides of the spine section, the plane of each lobe being disposed at an angle to a transverse radial plane normal to the opposite longitudinal edges of the spine section whereby the lobes on one side are all disposed in a direction opposite the lobes on the opposite side, and whereby the alined lobed apertures on opposite sides of the spine section are asymmetrically arranged with respect to the axis of the spine section.

The hereinshown agitator strip embodying this concept comprises, a spine section B from the opposite faces of which lobes l are struck out.

Because this agitator strip must be capable of being occasionally removed and replaced to permit cleaning thereof, and the tube wherein it is used, it is imperative that the spine section 6 possess an inherent self-rigidity that makes practical the aforesaid handling, particularly with unskilled and often careless workmen. Such rigidity might be attained merely by the thickness of the material per so from which the agitator strip is formed. However, to insure that self-rigidity, and also to make practical use of the lightest possible material, a spine section 6 with lateral flanges 8 is preferred. These flanges 8 might be disposed in the same direction on one side of the body of the spine section 5, thus making a channel-shaped spine section. However, the opposite disposition of the flanges 8 has been found more expedient, thus making the spine section E3 substantially Z-shaped as hereinshown. Obviously the flanges 8 would be curved so that the overall outside diameter of the spine section would be approximately the same as the internal diameter of the tube 9 wherewith the agitator is to be used. The difference in these two diameters would need to be only a few thousandths of an inch to permit easy insertion of the agitator strip into a tube and removal therefrom and at the same time insure a virtual 1netal-to-metal contact, when the agitator strip was in place in the tube, so as to facil itate the conduction of heat from the inner concentric films or laminae of oil through the lobes 1 and spine section 6 and the flanges 8 to the wall of the tube Q.

The lobes '2 are here shown of substantially arcuate form, each lobe being provided with an aperture H. Alternate lobes are struck out from opposite sides of the spine section 6. The angularity of these lobes l to the spine section 5 is an important factor in this improved agitator strip. The plane of each lobe I preferably is disposed at a right angle to the plane of the spine section 6, as most clearly illustrated. in Fig. 5. On the other hand the plane of each lobe is disposed at a slight angle or incline to a transverse radial plane normal to the opposite longitudinal edges of the spine section (see lines P--P and L-L of Fig. 2). Thus, the lobes l on one side of the spine section 6 have a common slant or inclination opposite that of the lobes on the opposite side of the spine section 6, which is most evident from Fig. 2. This inclination of the lobes was determined upon on the theorywhich has been demonstrated by tests--that a more ready axial flow of the oil through the tube with adequate longitudinal and transverse bafiling would be obtained than if the plane of the lobes 1 were coincident with a transverse axial normal plane. Moreover, the form and disposition of the lobes is such that the peripheral portions mostremote from the spine section are disposed in a circumference embracing the opposite edges of the spine section as most clearly shown in Fig. 4. Thus the lobes at these points have very close proximity if not actual contact with the inner face of the tube9.

The punchingout of a lobe l forms an opening Hi adjacent each lobe through which oil is baffled radially of the tube by the respective lobe 7.

The apertures H are punched in the lobes I substantially centrally of the perimeters of the respective lobes and the spine section. Obvious ly, the apertures H are punched out before the lobes I are struck out from the spine section 6. Thus, in the finished agitator, the alined axes of the apertures H on one side of the spine section 5 are asymmetrical of the lobe apertures on the other side, as is most apparent from Fig.4.

Agitator strips of the required length are cut from long sections of material after the forming thereof in the presses. The end of the spine section-t of such a strip is flared outwardly as indicated at 5'5 in Figs. 2 and 3. This flared end II will include a lobe 1' with its aperture II. The flaring of the end however will dispose the lobe l in the plane of the flared end l5, as is quite apparent from Fig. 3. This apertured, flared end serves a dual purpose. It limits the distance which the agitator strip may be inserted in a tube and it permits a tool to be inserted through the aperture ii when the agitator strip is to be removed from its tube 53.

Tests that have been made appear to substantiate the belief that oil passin through a tube containing such an agitator strip tends simultaneously to traverse three somewhat distinct yet constantly intermixing paths. Two of these paths are more or less axial of the tube 9 one along the flanges of the spine section 5 close to the wall of the tube, as indicated by the full-line arrows [2 in Fig. 2, and a second through the alined apertures H, as indicated by the dotted arrows it in 2 and 3. A third path is of a serpentine nature being successively forth and back axially of the tube and forth and back radially resulting from the baffling caused by the lobes l, as indicated by the dot-and-dash arrows M in Fig. 3. It is this slanted turbulent flow that is believed to be so effective in causing a high temperature drop in a tube equipped with an agitator strip of this kind. As is quite clear from Fig. 3 the lobes arrest the pressured axial flow backing it up slightly as it is directed through the openings It and then directed with some force against the wall of the tube 9. This tends to disperse the inner films or laminae of the oil column outwardly against the tube wall to mix with the axial flow path between the lobes l and the tube wall.

The fact that these lobes are inclined, as heretofore described, tends to more readily ease the baiiied inner currents into the outer axial currents to escape around the peripheries of the lobes adjacent the spine section flanges ii and mingle with the previously-mentioned axial flow represented by the arrows 52. This it is believed accounts for the low pressure drop concurrent with the high temperature drop obtained in practice with agitator strips embodying this invention.

Variations and modifications in the details of structure and arrangement of the parts may be resorted to within the spirit and coverage of the appended claims.

We claim:

1. An agitator for tubular heat exchangers comprising, a spine section having arcuateshaped lobes struck out transversely therefrom with the plane of each lobe disposed at an angle to a transverse radial plane normal to the opposite edges of the spine section and with the peripheral portions of the lobes most remote from the spine section disposed in a circumference embracing the opposite edges of the spine section.

2. An agitator for tubular heat exchangers comprising, a spine section formed of comparatively rigid material and having lobes struck out transversely therefrom substantially at right angles to the longitudinal plane of the spine section and with the plane of each lobe disposed at an angle to a transverse radial plane normal to the opposite longitudinal edges of the spine section and with the planes of alternate lobes oppositely disposed with respect to the respective radial plane.

3. An agitator for tubular heat exchangers comprising, a spine section formed of comparatively rigid material and having arcuate-shaped lobes struck out transversely therefrom and each lobe having an aperture formed therein substantially centrally of the perimeter of the lobe and the spine section, the lobes being disposed with the plane of each at an angle to a transverse radial plane normal to the opposite longitudinal edges of the spine section and with the planes of alternate lobes oppositely disposed with respect to the respective transverse radial planes.

4. An agitator for tubular heat exchangers comprising, a spine section flanged along its lateral edges to impart a high degree of rigidity thereto and having arcuate-shaped lobes struck out transversely therefrom substantially at right angles to the longitudinal plane of the spine section and with the plane of each lobe disposed at an angle to a transverse radial plane normal to the opposite longitudinal edges of the spine section and with the planes of alternate lobes oppositely disposed with respect to the respective transverse radial plane.

5. An agitator for tubular heat exchangers comprising, a spine section having lobes struck out transversely therefrom with the plane of each lobe disposed at an angle to a transverse radial plane normal to the opposite longitudinal edges of the spine section, one end of the spine section being flared to a Width greater than that of the spine section and apertured for the insertion of a tool for use in inserting the agitator in and removing it from a tube.

6. An agitator for tubular heat exchangers comprising, a Z-shaped spine section and having arcuate-shaped lobes struck out transversely therefrom and each lobe having an aperture formed therein substantially centrally of the perimeter of the lobe and the spine section, the lobes being disposed with the plane of each at an angle to a transverse radial plane normal to the opposite longitudinal edges of the spine section and with the planes of the alternate lobes oppositely disposed with respect to the respective transverse radial plane.

7. An agitator for tubular heat exchangers comprising a spine section having lobes struck out transversely therefrom on opposite sides substantially at right angles to the longitudinal plane of the spine section with the planes of the I respective lobes on one side of the spine section disposed at a common angle inclined to a transverse radial plane normal to the opposite edges of the spine section and with the planes of the respective lobes on the other side of the spine section also disposed at a common angle inclined to a transverse radial plane normal to the opposite edges of the spine section the common angle of the second lobes being opposite to the common angle of the first lobes.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,056,373 Segelken Mar. 18, 1913 2,091,274 Eggleston Aug. 31, 1937 2,096,272 Young Oct, 19, 1937 2,289,097 Brinen July 7, 1942 2,480,706 Brinen Aug. 30, 1949 FOREIGN PATENTS Number Country Date 99,486 Sweden July 30, 1940 331,602 Great Britain July 10, 1930 680,070 Germany Feb. 16, 1938 

